When is a government secret no longer a secret? Generally, when it shows up at the National Archives, that's one pretty good clue.

Then again, maybe not. In a program that predates the secretive Bush administration, the nation's intelligence agencies have been taking thousands of declassified documents out of the archives, essentially making them secrets again.

Hadn't heard about that? That's because the program itself is a secret.

According to a story in The New York Times, the push to pull documents is a backlash -- stronger since 9/11 -- against a Clinton-era executive order that made it harder to keep secrets more than 25 years old.

So now about 30 government workers spend each day going over old archived papers in search of ones that should be made secrets again. So far, more than 55,000 pages have been hidden again from public view, at a cost in the millions of dollars, according to The Times. The purge would've remained a secret, but a historian stumbled across signs of your tax dollars at work.

Nobody wants sensitive material available to just anybody. But some documents were yanked not to protect state secrets, but to avoid embarrassment. Like the 1950 CIA assessment that the Chinese were unlikely to intervene in the Korean War, written two weeks before 300,000 Chinese troops did just that. Or the 1948 memo about using balloons to drop propaganda leaflets in Eastern Europe.

Both of those are gone from the archives. It's hard to know much more about the program, since officials there are generally forbidden from talking about it, or even who's involved. According to one expert quoted by The Times, the secrecy is coming from the intelligence agencies, rather than directly from the White House.

A CIA spokesman said that the agency is just double-checking, and fixing mistakes made in earlier releases. A spokesman for the Defense Intelligence Agency refused to even admit the Pentagon was involved.